Oolitic beach barriers of the last Glacial sea-level lowstand at the outer Bengal shelf

During RV Sonne cruise 93 the Bengal shelf was surveyed using sediment echosounding, side-scan sonar and sediment coring techniques. A sequence of shallow ridges was discovered, each between 100 m and 260 m wide and extending for kilometres parallel to the 120–130-m isobaths. The ridges mark the top of a barely covered regressive sediment sequence and consist of oolitic limestone of Late Pleistocene age. They are interpreted as contouring fossil shorelines of sea-level lowstands of the Last Glacial Maximum. Their lithology indicates that fine-grained sediment supplied by the Ganges/Brahmaputra river system did not `pollute' the nearshore environment during Glacial times; this argues for sediment bypassing of the Bengal shelf and a direct supply to the Bengal deep-sea fan.